955Friction Stir Welding

Friction stir welding (FSW) is a new technique by which a nonconsumable tool is rotated and plunged into the joint made by abutting parts. The tool then moves along the joint, plasticizing the material to join it. No filler or shielding gas is needed, nor is there any need for current or voltage controls, and no welding fumes are produced. It has been applied to 2xxx, 5xxx, 6xxx and 7xxx alloys, in thicknesses up to 1 in. (25 mm). Friction stir welding produces uniform welds with little heat input and attendant distortion and loss of strength. The disadvantage is that high pressures must be brought to bear on the work, so the work must be properly supported and parts designed with this in mind. Commercial applications include rocket fuel tanks and ship decks. FSW is especially suited to making butt welds in long joints that are mass produced.